Support checking for qt5 instead of qt4 on Gentoo

hpcheck on Gentoo reports the following:

 error: python3-pyqt4-dbus PyQt 4 DBus - DBus Support for PyQt4 OPTIONAL 4.0 - MISSING 'python3-pyqt4-dbus needs to be installed'
 error: python3-pyqt4 PyQt 4- Qt interface for Python (for Qt version 4.x) REQUIRED 4.0 - MISSING 'python3-pyqt4 needs to be installed'

Which is obvious as Gentoo long switched to qt5.

I initially thought checking qt4 or qt5 is dependent on the ui_toolkit entry in installer/distros.dat So I set ui_toolkit=qt5 instead of ui_toolkit=none but hpcheck still checks for qt4.

I looked for other ways and changed the following:

--- hplip-3.20.5_orig/installer/core_install.py 2020-05-10 09:51:22.685158104 +0200
+++ hplip-3.20.5/installer/core_install.py 2020-05-10 14:18:41.840472948 +0200
@@ -762,7 +762,7 @@
         self.native_cups = self.get_distro_ver_data('native_cups', False)

         # Adjust required flag based on the distro ver ui_toolkit value
- ui_toolkit = self.get_distro_ver_data('ui_toolkit', 'qt4').lower()
+ ui_toolkit = self.get_distro_ver_data('ui_toolkit', 'qt5').lower()

         if ui_toolkit == 'qt4':
             log.debug("Default UI toolkit: Qt4")

Now hpcheck tries for qt5 instead but I think it is doing so in any case which is probably not a good solution as there are maybe distros out there still using qt4.

Would be great if this could be fixed so it works in a universally.